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15 pages, 8497 KiB

Open AccessArticle

Desert Environments Facilitate Unique Evolution of Biosynthetic Potential in Streptomyces

by Kunjukrishnan Kamalakshi Sivakala, Karina Gutiérrez-García, Polpass Arul Jose, Thangadurai Thinesh, Rangasamy Anandham, Francisco Barona-Gómez and Natesan Sivakumar

Molecules 2021, 26(3), 588; https://doi.org/10.3390/molecules26030588 - 22 Jan 2021

Cited by 13 | Viewed by 3483

Abstract

Searching for new bioactive metabolites from the bacterial genus Streptomyces is a challenging task. Combined genomic tools and metabolomic screening of Streptomyces spp. native to extreme environments could be a promising strategy to discover novel compounds. While Streptomyces of desertic origin have been [...] Read more.

Searching for new bioactive metabolites from the bacterial genus Streptomyces is a challenging task. Combined genomic tools and metabolomic screening of Streptomyces spp. native to extreme environments could be a promising strategy to discover novel compounds. While Streptomyces of desertic origin have been proposed as a source of new metabolites, their genome mining, phylogenetic analysis, and metabolite profiles to date are scarcely documented. Here, we hypothesized that Streptomyces species of desert environments have evolved with unique biosynthetic potential. To test this, along with an extensive characterization of biosynthetic potential of a desert isolate Streptomyces sp. SAJ15, we profiled phylogenetic relationships among the closest and previously reported Streptomyces of desert origin. Results revealed that Streptomyces strains of desert origin are closer to each other and relatively distinct from Streptomyces of other environments. The draft genome of strain SAJ15 was 8.2 Mb in size, which had 6972 predicted genes including 3097 genes encoding hypothetical proteins. Successive genome mining and phylogenetic analysis revealed the presence of putative novel biosynthetic gene clusters (BGCs) with low incidence in another Streptomyces. In addition, high-resolution metabolite profiling indicated the production of arylpolyene, terpenoid, and macrolide compounds in an optimized medium by strain SAJ15. The relative abundance of different BGCs in arid Streptomyces differed from the non-arid counterparts. Collectively, the results suggested a distinct evolution of desert Streptomyces with a unique biosynthetic potential. Full article

(This article belongs to the Special Issue Microbial Natural Products)

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15 pages, 3037 KiB

Open AccessFeature PaperArticle

Exopolysaccharide II Is Relevant for the Survival of Sinorhizobium meliloti under Water Deficiency and Salinity Stress

by Emiliano Primo, Pablo Bogino, Sacha Cossovich, Emiliano Foresto, Fiorela Nievas and Walter Giordano

Molecules 2020, 25(21), 4876; https://doi.org/10.3390/molecules25214876 - 22 Oct 2020

Cited by 10 | Viewed by 2414

Abstract

Sinorhizobium meliloti is a soil bacterium of great agricultural importance because of its ability to fix atmospheric nitrogen in symbiotic association with alfalfa (Medicago sativa) roots. We looked into the involvement of exopolysaccharides (EPS) in its survival when exposed to different [...] Read more.

Sinorhizobium meliloti is a soil bacterium of great agricultural importance because of its ability to fix atmospheric nitrogen in symbiotic association with alfalfa (Medicago sativa) roots. We looked into the involvement of exopolysaccharides (EPS) in its survival when exposed to different environmental stressors, as well as in bacteria–bacteria and bacteria–substrate interactions. The strains used were wild-type Rm8530 and two strains that are defective in the biosynthesis of EPS II: wild-type Rm1021, which has a non-functional expR locus, and mutant Rm8530 expA. Under stress by water deficiency, Rm8530 remained viable and increased in number, whereas Rm1021 and Rm8530 expA did not. These differences could be due to Rm8530′s ability to produce EPS II. Survival experiments under saline stress showed that viability was reduced for Rm1021 but not for Rm8530 or Rm8530 expA, which suggests the existence of some regulating mechanism dependent on a functional expR that is absent in Rm1021. The results of salinity-induced stress assays regarding biofilm-forming capacity (BFC) and autoaggregation indicated the protective role of EPS II. As a whole, our observations demonstrate that EPS play major roles in rhizobacterial survival. Full article

(This article belongs to the Special Issue Microbial Natural Products)

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16 pages, 3683 KiB

Open AccessArticle

Attraction of Adults of Cyclocephala lunulata and Cyclocephala barrerai (Coleoptera: Scarabaeoidea: Melolonthidae) towards Bacteria Volatiles Isolated from Their Genital Chambers

by Abraham Sanchez-Cruz, Norma Robledo, María Rosete-Enríquez and Angel A. Romero-López

Molecules 2020, 25(19), 4430; https://doi.org/10.3390/molecules25194430 - 27 Sep 2020

Cited by 5 | Viewed by 2609

Abstract

In the study of the chemical communication of adults of the Melolonthidae family, bacteria have been observed in the epithelium of the genital chamber; possibly, bacteria are involved in the production of sex attractants in their hosts. Therefore, it is important to identify [...] Read more.

In the study of the chemical communication of adults of the Melolonthidae family, bacteria have been observed in the epithelium of the genital chamber; possibly, bacteria are involved in the production of sex attractants in their hosts. Therefore, it is important to identify the volatile organic compounds from bacteria (VOCsB) released by these microorganisms and study the biological activity stimulated by VOBCs in adults of Melolonthidae. In this study, bacteria were isolated from the genital chamber of Cyclocephala lunulata and Cyclocephala barrerai, from which VOCsB were extracted using static headspace solid-phase microextraction (SHS-SPME) and dynamic headspace Super Q solid-phase extraction (DHS-SPE) and analyzed using gas chromatography-mass spectrometry. The effect of VOCsB on the hosts and conspecifics was evaluated utilizing an olfactometer and electroantennography (EAG). Two species of Enterobacteria were isolated from the genital chamber of each female species, and VOCsB derived from sulfur-containing compounds, alcohols, esters, and fatty acids were identified. An attraction response was observed in olfactometry studies, and antennal responses to VOCsB were confirmed in EAG bioassays. With these results, new perspectives on the relationship between these beetles and their bacteria emerge, in addition to establishing a basis for management programs in the future. Full article

(This article belongs to the Special Issue Microbial Natural Products)

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14 pages, 1163 KiB

Open AccessArticle

Isolation and Antibacterial Activity of Indole Alkaloids from Pseudomonas aeruginosa UWI-1

by Antonio Ramkissoon, Mohindra Seepersaud, Anderson Maxwell, Jayaraj Jayaraman and Adesh Ramsubhag

Molecules 2020, 25(16), 3744; https://doi.org/10.3390/molecules25163744 - 17 Aug 2020

Cited by 19 | Viewed by 3734

Abstract

In this study, we report the first isolation of three antibiotic indole alkaloid compounds from a Pseudomonad bacterium, Pseudomonas aeruginosa UWI-1. The bacterium was batch fermented in a modified Luria Broth medium and compounds were solvent extracted and isolated by bioassay-guided fractionation. The [...] Read more.

In this study, we report the first isolation of three antibiotic indole alkaloid compounds from a Pseudomonad bacterium, Pseudomonas aeruginosa UWI-1. The bacterium was batch fermented in a modified Luria Broth medium and compounds were solvent extracted and isolated by bioassay-guided fractionation. The three compounds were identified as (1) tris(1H-indol-3-yl) methylium, (2) bis(indol-3-yl) phenylmethane, and (3) indolo (2, 1b) quinazoline-6, 12 dione. A combination of 1D and 2D NMR, high-resolution mass spectrometry data and comparison from related data from the literature was used to determine the chemical structures of the compounds. Compounds 1–3 were evaluated in vitro for their antimicrobial activities against a wide range of microorganisms using the broth microdilution technique. Compounds 1 and 2 displayed antibacterial activity against only Gram-positive pathogens, although 1 had significantly lower minimum inhibitory concentration (MIC) values than 2. Compound 3 displayed potent broad-spectrum antimicrobial activity against a range of Gram positive and negative bacteria. Several genes identified from the genome of P. aeruginosa UWI-1 were postulated to contribute to the biosynthesis of these compounds and we attempted to outline a possible route for bacterial synthesis. This study demonstrated the extended metabolic capability of Pseudomonas aeruginosa in synthesizing new chemotypes of bioactive compounds. Full article

(This article belongs to the Special Issue Microbial Natural Products)

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14 pages, 2320 KiB

Open AccessArticle

Identification of Secondary Metabolites from Aspergillus pachycristatus by Untargeted UPLC-ESI-HRMS/MS and Genome Mining

by Bruno Perlatti, Nan Lan, Yongying Jiang, Zhiqiang An and Gerald Bills

Molecules 2020, 25(4), 913; https://doi.org/10.3390/molecules25040913 - 18 Feb 2020

Cited by 2 | Viewed by 3980

Abstract

Aspergillus pachycristatus is an industrially important fungus for the production of the antifungal echinocandin B and is closely related to model organism A. nidulans. Its secondary metabolism is largely unknown except for the production of echinocandin B and sterigmatocystin. We constructed mutants [...] Read more.

Aspergillus pachycristatus is an industrially important fungus for the production of the antifungal echinocandin B and is closely related to model organism A. nidulans. Its secondary metabolism is largely unknown except for the production of echinocandin B and sterigmatocystin. We constructed mutants for three genes that regulate secondary metabolism in A. pachycristatus NRRL 11440, and evaluated the secondary metabolites produced by wild type and mutants strains. The secondary metabolism was explored by metabolic networking of UPLC-HRMS/MS data. The genes and metabolites of A. pachycristatus were compared to those of A. nidulans FGSC A4 as a reference to identify compounds and link them to their encoding genes. Major differences in chromatographic profiles were observable among the mutants. At least 28 molecules were identified in crude extracts that corresponded to nine characterized gene clusters. Moreover, metabolic networking revealed the presence of a yet unexplored array of secondary metabolites, including several undescribed fellutamides derivatives. Comparative reference to its sister species, A. nidulans, was an efficient way to dereplicate known compounds, whereas metabolic networking provided information that allowed prioritization of unknown compounds for further metabolic exploration. The mutation of global regulator genes proved to be a useful tool for expanding the expression of metabolic diversity in A. pachycristatus. Full article

(This article belongs to the Special Issue Microbial Natural Products)

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15 pages, 3472 KiB

Open AccessArticle

Interaction with Soil Bacteria Affects the Growth and Amino Acid Content of Piriformospora indica

by Jorge A. Leyva-Rojas, Ericsson Coy-Barrera and Rüdiger Hampp

Molecules 2020, 25(3), 572; https://doi.org/10.3390/molecules25030572 - 28 Jan 2020

Cited by 10 | Viewed by 3330

Abstract

Exploration of the effect of soil bacteria on growth and metabolism of beneficial root endophytic fungi is relevant to promote favorable associations between microorganisms of the plant rhizosphere. Hence, the interaction between the plant-growth-promoting fungus Piriformospora indica and different soil bacteria was investigated. [...] Read more.

Exploration of the effect of soil bacteria on growth and metabolism of beneficial root endophytic fungi is relevant to promote favorable associations between microorganisms of the plant rhizosphere. Hence, the interaction between the plant-growth-promoting fungus Piriformospora indica and different soil bacteria was investigated. The parameters studied were fungal growth and its amino acid composition during the interaction. Fungus and bacteria were confronted in dual cultures in Petri dishes, either through agar or separated by a Perspex wall that only allowed the bacterial volatiles to be effective. Fungal growth was stimulated by Azotobacter chroococcum, whereas Streptomyces anulatus AcH 1003 inhibited it and Streptomyces sp. Nov AcH 505 had no effect. To analyze amino acid concentration data, targeted metabolomics was implemented under supervised analysis according to fungal-bacteria interaction and time. Orthogonal partial least squares-discriminant analysis (OPLS-DA) model clearly discriminated P. indica–A. chroococcum and P. indica–S. anulatus interactions, according to the respective score plot in comparison to the control. The most observable responses were in the glutamine and alanine size groups: While Streptomyces AcH 1003 increased the amount of glutamine, A. chroococcum decreased it. The fungal growth and the increase of alanine content might be associated with the assimilation of nitrogen in the presence of glucose as a carbon source. The N-fixing bacterium A. chroococcum should stimulate fungal amino acid metabolism via glutamine synthetase-glutamate synthase (GS-GOGAT). The data pointed to a stimulated glycolytic activity in the fungus observed by the accumulation of alanine, possibly via alanine aminotransferase. The responses toward the growth-inhibiting Streptomyces AcH 1003 suggest an (oxidative) stress response of the fungus. Full article

(This article belongs to the Special Issue Microbial Natural Products)

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11 pages, 997 KiB

Open AccessArticle

Chemical Composition and Biological Activities of Metabolites from the Marine Fungi Penicillium sp. Isolated from Sediments of Co To Island, Vietnam

by Hong Minh Thi Le, Quynh Thi Do, Mai Huong Thi Doan, Quyen Thi Vu, Mai Anh Nguyen, Thu Huyen Thi Vu, Hai Dang Nguyen, Nguyen Thi Thuy Duong, Manh Hung Tran, Van Minh Chau and Van Cuong Pham

Molecules 2019, 24(21), 3830; https://doi.org/10.3390/molecules24213830 - 24 Oct 2019

Cited by 10 | Viewed by 3457

Abstract

Marine microorganisms are an invaluable source of novel active secondary metabolites possessing various biological activities. In this study, the extraction and isolation of the marine sediment Penicillium species collected in Vietnam yielded ten secondary metabolites, including sporogen AO-1 (1), 3-indolecarbaldehyde ( [...] Read more.

Marine microorganisms are an invaluable source of novel active secondary metabolites possessing various biological activities. In this study, the extraction and isolation of the marine sediment Penicillium species collected in Vietnam yielded ten secondary metabolites, including sporogen AO-1 (1), 3-indolecarbaldehyde (2), 2-[(5-methyl-1,4-dioxan-2-yl)methoxy]ethanol (3), 2-[(2R-hydroxypropanoyl)amino]benzamide (4), 4-hydroxybenzandehyde (5), chrysogine (6), 3-acetyl-4-hydroxycinnoline (7), acid 1H-indole-3-acetic (8), cyclo (Tyr-Trp) (9), and 2’,3’-dihydrosorbicillin (10). Their structures were identified by the analysis of 1D and 2D NMR data. Among the isolated compounds, 2-[(5-methyl-1,4-dioxan-2-yl)methoxy]ethanol (3) showed a strong inhibitory effect against Enterococcus faecalis with a minimum inhibitory concentration value of 32 µg/mL. Both 2-[(2R-hydroxypropanoyl)amino]benzamide (4) and 4-hydroxybenzandehyde (5) selectively inhibited E. coli with minimum inhibitory concentration values of 16 and 8 µg/mL, respectively. 2’,3’-Dihydrosorbicillin (10) potentially inhibited α-glucosidase activity at a concentration of 2.0 mM (66.31%). Full article

(This article belongs to the Special Issue Microbial Natural Products)

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9 pages, 2636 KiB

Open AccessArticle

Chaetomadrasins A and B, Two New Cytotoxic Cytochalasans from Desert Soil-Derived Fungus Chaetomium madrasense 375

by Qing-Feng Guo, Zhen-Hua Yin, Juan-Juan Zhang, Wen-Yi Kang, Xue-Wei Wang, Gang Ding and Lin Chen

Molecules 2019, 24(18), 3240; https://doi.org/10.3390/molecules24183240 - 05 Sep 2019

Cited by 22 | Viewed by 2986

Abstract

Two new cytochalasans, Chaetomadrasins A (1) and B (2), along with six known analogues (3–8), were isolated from the solid-state fermented culture of desert soil-derived Chaetomium madrasense 375. Their structures were clarified by comprehensive spectroscopic [...] Read more.

Two new cytochalasans, Chaetomadrasins A (1) and B (2), along with six known analogues (3–8), were isolated from the solid-state fermented culture of desert soil-derived Chaetomium madrasense 375. Their structures were clarified by comprehensive spectroscopic analyses, and the absolute configurations of Compounds 1 and 2 were confirmed by electronic circular dichroism (ECD) and calculated ECD. For the first time, Chaetomadrasins A (1), which belongs to the chaetoglobosin family, is characterized by the presence of all oxygen atoms in the form of Carbonyl. Chaetomadrasin B (2) represents the first example of chaetoglobosin type cytochalasan characterized by a hydroxy unit and carbonyl group fused to the indole ring. Compounds 1 and 2 displayed moderate cytotoxicity against HepG2 human hepatocellular carcinoma cells. Full article

(This article belongs to the Special Issue Microbial Natural Products)

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11 pages, 1791 KiB

Open AccessArticle

Broad-Spectrum Antiviral Natural Products from the Marine-Derived Penicillium sp. IMB17-046

by Jiao Li, Yujia Wang, Xiaomeng Hao, Shasha Li, Jia Jia, Yan Guan, Zonggen Peng, Hongkai Bi, Chunling Xiao, Shan Cen and Maoluo Gan

Molecules 2019, 24(15), 2821; https://doi.org/10.3390/molecules24152821 - 02 Aug 2019

Cited by 29 | Viewed by 4477

Abstract

A new pyrazine derivative, trypilepyrazinol (1), a new α-pyrone polyketide, (+)-neocitreoviridin (2), and a new ergostane analogue, 3β-hydroxyergosta-8,14,24(28)-trien-7-one (3), were isolated and characterized along with five known compounds from the marine-derived fungus Penicillium sp. IMB17-046. The structures [...] Read more.

A new pyrazine derivative, trypilepyrazinol (1), a new α-pyrone polyketide, (+)-neocitreoviridin (2), and a new ergostane analogue, 3β-hydroxyergosta-8,14,24(28)-trien-7-one (3), were isolated and characterized along with five known compounds from the marine-derived fungus Penicillium sp. IMB17-046. The structures of these new compounds were determined using spectroscopic data analyses (HRESIMS, 1D- and 2D-NMR), X-ray crystallography analysis, and TDDFT ECD calculation. Compounds 1 and 3 exhibited broad-spectrum antiviral activities against different types of viruses, including human immunodeficiency virus (HIV), hepatitis C virus (HCV), and influenza A virus (IAV), with IC₅₀ values ranging from 0.5 to 7.7 μM. Compounds 1 and 2 showed antibacterial activities against Helicobacter pylori, a causative pathogen of various gastric diseases, with minimum inhibitory concentration (MIC) values of 1–16 μg/mL. Full article

(This article belongs to the Special Issue Microbial Natural Products)

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13 pages, 3479 KiB

Open AccessArticle

New Butenolides and Cyclopentenones from Saline Soil-Derived Fungus Aspergillus Sclerotiorum

by Li-Ying Ma, Huai-Bin Zhang, Hui-Hui Kang, Mei-Jia Zhong, De-Sheng Liu, Hong Ren and Wei-Zhong Liu

Molecules 2019, 24(14), 2642; https://doi.org/10.3390/molecules24142642 - 21 Jul 2019

Cited by 7 | Viewed by 2970

Abstract

Three new γ-hydroxyl butenolides (1–3), a pair of new enantiomeric spiro-butenolides (4a and 4b), a pair of enantiomeric cyclopentenones (5a new and 5b new natural), and six known compounds (6–11), were [...] Read more.

Three new γ-hydroxyl butenolides (1–3), a pair of new enantiomeric spiro-butenolides (4a and 4b), a pair of enantiomeric cyclopentenones (5a new and 5b new natural), and six known compounds (6–11), were isolated from Aspergillus sclerotiorum. Their structures were established by spectroscopic data and electronic circular dichroism (ECD) spectra. Two pairs of enantiomers [(+)/(–)-6c and (+)/(–)-6d] obtained from the reaction of 6 with acetyl chloride (AcCl) confirmed that 6 was a mixture of two pairs of enantiomers. In addition, the X-ray data confirmed that 7 was also a racemate. The new metabolites (1−5) were evaluated for their inhibitory activity against cancer and non-cancer cell lines. As a result, compound 1 exhibited moderate cytotoxicity to HL60 and A549 with IC₅₀ values of 6.5 and 8.9 µM, respectively, and weak potency to HL-7702 with IC₅₀ values of 17.6 µM. Furthermore, compounds 1−9 were screened for their antimicrobial activity using the micro-broth dilution method. MIC values of 200 μg/mL were obtained for compounds 2 and 3 towards Staphylococcus aureus and Escherichia coli, while compound 8 exhibited a MIC of 50 μ/mL towards Candida albicans. Full article

(This article belongs to the Special Issue Microbial Natural Products)

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11 pages, 2757 KiB

Open AccessArticle

Insights into Triterpene Acids in Fermented Mycelia of Edible Fungus Poria cocos by a Comparative Study

by Jian Jin, Rongrong Zhou, Jing Xie, Huixuan Ye, Xuejuan Liang, Can Zhong, Bingbing Shen, You Qin, Shuihan Zhang and Luqi Huang

Molecules 2019, 24(7), 1331; https://doi.org/10.3390/molecules24071331 - 04 Apr 2019

Cited by 16 | Viewed by 4571

Abstract

As an edible sclerotia-forming fungus, Poria cocos is widely used as a food supplement and as a tonic in China. High-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (HPLC-QTOF-MS/MS) was applied to identify triterpene acids in fermented mycelia of P. cocos, as well as the [...] Read more.

As an edible sclerotia-forming fungus, Poria cocos is widely used as a food supplement and as a tonic in China. High-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (HPLC-QTOF-MS/MS) was applied to identify triterpene acids in fermented mycelia of P. cocos, as well as the epidermis and inner part of natural sclerotia. A total of 19 triterpene acids were identified in fermented mycelia, whereas 31 were identified in the epidermis and 24 in the inner part. Nine triterpene acids were quantitatively determined, and the concentrations of two valuable triterpenes, dehydropachymic acid and pachymic acid, reached 1.07 mg/g and 0.61 mg/g in the fermented mycelia part, respectively, and were both significantly higher than the concentration in the two natural parts. The fermented mycelia could be a good choice for producing some target triterpene compounds and functional foods through fermentation thanks to the high concentration of some triterpene acids. Full article

(This article belongs to the Special Issue Microbial Natural Products)

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Review

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35 pages, 2128 KiB

Open AccessReview

Terrestrial Microorganisms: Cell Factories of Bioactive Molecules with Skin Protecting Applications

by Laure-Anne Peyrat, Nikolaos Tsafantakis, Katerina Georgousaki, Jamal Ouazzani, Olga Genilloud, Ioannis P. Trougakos and Nikolas Fokialakis

Molecules 2019, 24(9), 1836; https://doi.org/10.3390/molecules24091836 - 13 May 2019

Cited by 17 | Viewed by 6920

Abstract

It is well known that terrestrial environments host an immense microbial biodiversity. Exposed to different types of stress, such as UV radiation, temperature fluctuations, water availability and the inter- / intra-specific competition for resources, terrestrial microorganisms have been evolved to produce a large [...] Read more.

It is well known that terrestrial environments host an immense microbial biodiversity. Exposed to different types of stress, such as UV radiation, temperature fluctuations, water availability and the inter- / intra-specific competition for resources, terrestrial microorganisms have been evolved to produce a large spectrum of bioactive molecules. Bacteria, archaea, protists, fungi and algae have shown a high potential of producing biomolecules for pharmaceutical or other industrial purposes as they combine a sustainable, relatively low-cost and fast-production process. Herein, we provide an overview of the different bioactive molecules produced by terrestrial microorganisms with skin protecting applications. The high content in polyphenolic and carotenoid compounds produced by several strains, as well as the presence of exopolysaccharides, melanins, indole and pyrrole derivatives, mycosporines, carboxylic acids and other molecules, are discussed in the context of their antioxidant, photo-protective and skin-whitening activity. Relevant biotechnological tools developed for the enhanced production of high added value natural products, as well as the protecting effect of some antioxidant, hydrolytic and degrading enzymes are also discussed. Furthermore, we describe classes of microbial compounds that are used or have the potential to be used as antimicrobials, moisturizers, biosurfactants, pigments, flavorings and fragrances. Full article

(This article belongs to the Special Issue Microbial Natural Products)

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